1. Field of the Invention
The present invention relates a zoom lens and an image pickup apparatus equipped with the same.
2. Description of the Related Art
In recent years, digital cameras that pick up an image of an object using a solid state image pickup element such as a CCD or CMOS have replaced film cameras and become the mainstream. Furthermore, various categories of digital cameras ranging from popular-priced compact type cameras to function-rich cameras for professionals have been developed.
Users of popular-priced digital cameras wish to enjoy easy shooting in various shooting situations anywhere at any time. For this reason, such users favor small size digital cameras, especially slim digital cameras that can be conveniently carried in a pocket of clothes or a bag. Therefore, a further reduction in the size of the taking lens system is demanded.
Moreover, while a wide angle of view is demanded in terms of the zoom range, image pickup apparatuses equipped with a zoom lens having a configuration that can be manufactured at low cost while having high optical performance with a zoom ratio higher than five are demanded.
As a zoom lens having a high zoom ratio and a relatively wide angle of view while being composed of a small number of lenses, there has been known a prior art zoom lens including, in order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power (see Japanese Patent Application Laid-open Nos. 2010-145587 and 2011-64933).
The optical systems disclosed in Japanese Patent Application Laid-open Nos. 2010-145587 and 2011-64933 have a zoom ratio of about 4.8 while having a wide angle of view. In an optical system according to an embodiment disclosed in Japanese Patent Application Laid-open No. 2010-145587 and an optical system according to an embodiment (embodiment 1) disclosed in Japanese Patent Application Laid-open No. 2011-64933, the third lens unit is composed on only one single lens, so that the number of lenses in the optical system is small.